1. Field of Invention
The field of the present invention relates in general to wireless local area networks including wireless access points (WAP) and wireless stations and methods of coordinating transmissions thereon.
2. Description of the Related Art
Enterprise wireless networks, a.k.a. wireless local area networks (WLAN) are established using multiple centrally controlled devices called Wireless Access Points (WAP)s. Each WAP wirelessly couples all associated devices, e.g. wireless stations such as: computers, printers, televisions, security cameras across the entire enterprise to one another and to the Internet. Most WAPs implement the IEEE 802.11 standard which is a contention based standard for handling communications among multiple competing devices for a shared wireless communication medium on a selected one of a plurality of communication channels. The frequency range of each communication channel is specified in the corresponding one of the protocols, e.g. “a”, “b”, “g”, “n”, “ac”, “ad” specified in the IEEE 802.11 standard. Communications follow a hub and spoke model with each WAP at the hub and the spokes corresponding to the wireless links to each ‘client’ device. A communication between from a transmitting WAP and one of its associated receiving stations is identified as a downlink communication. Conversely, a communication from a transmitting station to its receiving WAP with which it is associated is identified as an uplink communication.
After a central controller selects a communication channel for each WAP, access to the communication channel relies on a multiple access methodology identified as Collision Sense Multiple Access (CSMA). CSMA is a distributed random access methodology first introduced for home wired networks such as Ethernet for sharing a single communication medium, by having a contending communication link back off and retry access to the line if a collision is detected, i.e. if the wireless medium is in use. A WLAN operative in this manner is said to implement: CSMA\CA where the “CA” moniker signifies collision avoidance as the connectionless access coordination methodology.
Communications on the single communication medium are identified as “simplex” meaning, communications from a single source node to one target node at one time, with all remaining nodes capable of “listening” to the subject transmission. Starting with the IEEE 802.11ac standard and specifically ‘Wave 2’ thereof, discrete communications to more than one target node at the same time may take place using what is called Multi-User (MU) multiple-input multiple-output (MIMO) capability of the WAP. MU capabilities were added to the standard to enable the WAP to communicate with multiple single antenna single stream devices concurrently, thereby increasing the time available for discrete MIMO links to contending wireless devices.
An Enterprise WLAN may consist of hundreds or thousands of WAPs each supporting communications of hundreds of associated wireless communication devices and the Internet on its own sub-net and all collectively operating under control of the central controller. Each WAP uses the same Service Set Identifier (SSID) for station association. To increase network throughput the central controller will typically assign the different channels to selected subsets of the WAPS. This allows concurrent communications to take place on different channels while still maintaining compliance with the CSMA\CA protocol. Unfortunately, such throughput improvements achieved by frequency separation come at the price of decreased bandwidth for communications, which of course has its own countervailing effect on throughput. This tradeoff is particularly noticeable in the more recent IEEE 802.11 compliant protocols such as 802.11ac. This protocol allows channel aggregation of the many discrete 20 Mhz channels into aggregate channels totaling 160 Mhz. This broad bandwidth may be required for wireless video conferencing devices and other low latency high throughput enterprise devices. Thus the central controller is left with the tradeoffs between frequency separation between proximate WAPs at the price of decreased bandwidth.
What is needed are improved methods for increased throughput options on Enterprise wireless local area networks (WLAN).